1. Field
The following description relates to a Software Defined Radio (SDR) terminal, and more particularly, to a method and apparatus for allowing a Software Defined Radio (SDR) terminal to perform a vertical handover between different services.
2. Description of the Related Art
The structure of a Software Defined Radio (SDR) terminal is based on a Software Communication Architecture (SCA) core framework.
SCA is a standardized communication software proposed by the U.S. Joint Tactical System (JTRS) Joint Program Office (JPO) for the purpose of improving inter-operability between communication systems and reducing costs for development and design. A SDR system seeks high compatibility and inter-operability between configuration modules by adopting SCA as a software framework standard.
Vertical handover (VHO) means handover between different services. As mobile communication services diversify, there are cases where users who have subscribed with two or more mobile communication services. And, users want to get mobile communication services seamlessly while migrating between different mobile communication services as necessary.
For example, if a user who uses an IEEE 802.11 Wireless LAN (WLAN) indoors changes to the service of an IEEE 802.16e Mobile WiMAX service when he or she goes outdoors, then this means that a handover between the two services has occurred.
A recently proposed vertical handover, which is based on the IEEE 802.21 standard, locates Media Independent Handover (MIH) between a Medium Access Control (MAC) layer and a Layer 3 (L3) layer. Also, the method causes MIH to standardize and accept handover-associated primitives of various MAC layers for each media so that the L3 layer can control handover between services through a single method. The 802.21-based vertical handover enables seamless handover between a plurality of MAC/PHY protocols installed in advance under the control of a single MIH.
A SDR terminal is an open system designed to flexibly receive various communication services with a single piece of hardware. A SDR terminal has been initially provided in the is form of Bare Machine. A SDR terminal downloads protocols for a desired service as necessary, and then installs therein and executes them. The SDR terminal is expected to be a system which is flexibly adaptable to the current mobile communication environment including frequent creations and abandoning of various mobile communication services.
The 802.21-based vertical handover technique is structured under the basic assumption that protocol sets of relevant mobile communication services should be installed in a terminal. For example, when a vertical handover occurs between 802.11 and 802.16e, 802.11 MAC/PHY and 802.16e have to be installed in a corresponding terminal and be in a standby state for execution to respond to MIH commands. Accordingly, if the number of service objects that allow vertical handover is N, then N number of MAC/PHY protocols have to be installed in advance in the corresponding terminal.
However, in the 802.21-based vertical handover technique, since all protocols of all services with which a user subscribes have to be loaded into hardware, it may cause unnecessary waste of hardware resources, resulting in inefficient resource management. Also, since whenever a change occurs in use of service, such as service subscription or service secession, the corresponding set of protocols has to be newly installed or deleted, and as such an inconvenience with regards to required updates or replacements is created.
Meanwhile, in the case of the SDR terminal, there are advantages in that, when a service changes to another one, not too many protocols are required to be loaded and replacement of hardware is also not required. In order to perform a seamless vertical handover, a service that is to be handed over has to be recognized in advance. Otherwise, an additional time for installing an application service for a service that is to be handed over would be required. This is because a SDR terminal requires a time to download and install protocol sets of a required service. Consequently, since any time consumed to install new application services delay handover, continuity of service may not be ensured.